Download or read book Characterization of the Zr polymeryl Species Present During Ethylene and Propylene Polymerizations by Homogeneous Zirconocene Catalysts written by and published by . This book was released on 2008 with total page 428 pages. Available in PDF, EPUB and Kindle. Book excerpt: A detailed investigation of Zr-polymeryl intermediates, present during ethylene and propylene polymerization by metallocene and non-metallocene catalysts, is presented. In this regard, the potential use of bromine as a quenching agent to give polymers with brominated end groups is investigated. Using NMR spectroscopy, these groups can be identified as primary or secondary and quantified, thus providing information on the nature of the Zr-polymeryl linkage(s) and their relative concentration(s). Bromine quenching was examined for ethylene polymerization by Cp2ZrMe2/B(C6F5)3, and for propylene polymerization by Cp2ZrMe2/B(C6F5)3, (indenyl)2ZrMe2/B(C6F5)3, and rac-{C2H4(1-indenyl)2}ZrMe2/B(C6F5)3. Polymers with primary alkyl bromide end groups were obtained. In the case of propylene polymerization by [ONNO]Zr(CH2C6H5)2/MAO/2,6-di-tbutylphenol, both primary and secondary alkyl bromide end groups were detected. Primary alkyl bromide end groups result from the cleavage by bromine of primary Zr-CH2~polymeryl linkages while secondary alkyl bromides are the result of the cleavage by bromine of secondary Zr-CH(Me)CH2~polymeryl linkages. The concentration of Zr-CH2~polymeryl intermediates was found to be low, suggesting that the catalyst deactivates during the polymerization. A second objective of this research is to investigate the formation of Cp2Zr+-allyl complexes as these species are proposed to arise during the polymerization and deactivate the catalyst. Compounds of type [Cp2ZrMe]+ were found to react with vinylidene compounds of type CH2=C(Me)R, (R = CH2CHMe2 and CH2CH(Me)C3H7), to form methane and Cp2Zr+-allyl complexes. The reaction of Cp2ZrMe2/[Ph3C][B(C6F5)4] with CH2=C(Me)CH2CHMe2 involves the unprecedented [Cp2Zr(Me)(CH2CMeCH2CHMe2)]+ intermediate, detected by low temperature one- and two-dimensional NMR spectroscopy. The observation of this intermediate represents the first direct experimental evidence for a d0 metal-alkyl-olefin complex. The dynamic behavior and the kinetics of formation of Cp2Zr+-allyl complexes were also investigated by NMR spectroscopy. In situ propylene polymerization studies indicate that Cp2Zr+-allyl polymeryl intermediates form under catalytic conditions when either Cp2ZrMe2/B(C6F5)3 or Cp2ZrMe2/[Ph3C][B(C6F5)4] are used. Formation of Zr-allyl species occurs in the early stages of the polymerization process, even before the [Cp2ZrMe]+ catalyst is completely consumed, by recoordination of the polypropylene-containing vinylidene end groups, which are the normal products of chain transfer reactions via -H elimination, to the active catalyst.
Download or read book Characterization of the Zr polymeryl Species Present During Ethylene and Propylene Polymerizations by Homogeneous Zirconocene Catalysts written by MIHAELA. Vatamanu and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Supported 2 arylindenyl Zirconocene Polymerization Catalysts written by Stephen Christopher Diehl and published by . This book was released on 2000 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book New Aspects of Zirconium Containing Organic Compounds written by Ilan Marek and published by Springer Science & Business Media. This book was released on 2005-02-18 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: Metal carbene complexes have made their way from organometallic curiosities to valuable reagents and catalysts. They offer novel synthetic opportunities in carbon-carbon bond formation based on either carbene-centered reactions or on metal-templated processes which makes them indispensable in modern synthetic methodology. The most prominent metal carbenes are now either commercially available or easy to synthesize and handle with modern laboratory techniques. This volume organized in eight chapters written by the leading scientists in the field illustrates the theoretical background, non-classical nucleophilic and cycloaddition patterns, chromium-templated benzannulation and photo-induced reactions, rhodium-catalyzed carbene transfer as well as the principles and applications of olefin metathesis which has coined the progress in synthetic methodology over the past decade. Designed for researchers in academia and industry as well as graduate students it presents the state-of-the-art potential of carbene complexes in modern organic synthesis.
Download or read book Catalytic Properties of Zirconocene in Propylene Polymerization written by and published by . This book was released on 2000 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Structure selectivity Studies of Zirconium Catalysts in Ethylene alpha olefin Copolymerization written by Sarah Ellisse Reybuck and published by . This book was released on 2003 with total page 316 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Characteristics and Catalytic Properties of Silica supported Zirconocene MAO Catalysts for Ethylene Polymeriztion written by Piyarat Rodphon and published by . This book was released on 2011 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nowadays, the metallocene catalysts activated by methylaluminoxane are used in the synthesis of polyethylene because they give the high activity in ethylene polymerization. However these systems also have some big disadvantages such as the lack of morphology control. So, they need an excess amount of methylaluminoxane (MAO), which is very expensive. To overcome this drawback, the matallocene catalyst has to be attached on the support and also can be used in the slurry or gas-phase. In this research, silica as a support for metallocene catalyst system was studied. These studies were divided into two parts. In the first part, the copolymerization of ethylene/1-hexene with various the 1-hexene amount was investigated. The silica used in this part is in-house silica and the in situ impregnation was used in this part. It was found that when the amount of 1-hexene increased, the catalytic activity also increased. For the second part, the ex situ impregnation of methylaluminoxane on the commercial silica by varying the amount of methylaluminoxane was investigated. It can be seen the amounts of [Al]MAO on the commercial silica increased with increasing the amount of methylaluminoxane.
Download or read book Heterogenisation of zirconocene catalysts for ethylene polymerisation written by Sandra Turin and published by . This book was released on 2001 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Polymerization of Olefins and Functionalized Monomers with Zirconocene Catalysts written by Holger Frauenrath and published by . This book was released on 2001 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Synthesis and Characterization of III V Semiconductor Precursors and Homogeneous Catalysts for Olefin Polymerization written by Woo-Kyu Kim and published by . This book was released on 1998 with total page 410 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A High Throughput Experimental computational Investigation of Zirconium and Hafnium O4 Catalysts for Propene Polymerization written by Eric Cuthbert and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Group IV O4 catalysts are interesting due to their high activity, isotacticity and molecular weight capabilities for propene polymerization which justifies their use on commercial/industrial scales. However, these catalysts are not as well-studied in academic literature as they are reported in patent literature. This catalyst type is highly flexible which leaves the identity of active species undetermined. Furthermore, precisely how these catalysts exert control over insertion and chain termination reactions is not entirely understood. Computational chemistry has been used to study olefin polymerization catalysts and much understanding has been learned from this technique in a qualitative sense. As of writing this document, few attempts have been made to see if current methods can quantitatively reproduce experimental aspects such as tacticity, regioerrors and molecular weight of resultant polymers. In this thesis, we use a combined high-throughput experimentation (HTE) and high-throughput computation (HTC) approach to answer these uncertainties in the case of propene homopolymerization. A series of structurally different ligands were synthesized, complexed to zirconium and hafnium, then tested for propene polymerization with HTE reactors. Libraries of activities and propene microstructure were accumulated much quicker using less material than by traditional bottle polymerization. HTC was used to identify the active species, models of competing insertion/chain transfer transition states of the active species were matched to HTE data with high accuracy and provided extra insight than just from experiment alone. Traditional studies of coordination and activation chemistry demonstrated the influence of ligand choice: flexible and bulky ligands could make oligomeric products during chelation to metal while catalyst conformation is affected by ligand choice; these aspects are important to consider when designing tetradentate, octahedral catalysts to promote desirable active species equilibria and promote clean metal complexation. In summary, the combined HTE and HTC was successful for a deeper understanding of these catalysts. Our HTC results also demonstrate that it is possible to accurately model experiment with currently available methods. An important outlook of this work suggests that computational "pre-screening" of new catalysts may be beneficial: catalysts that would not produce desired polymer properties can be ruled out prior to resource-consuming synthesis and polymerization testing.
Download or read book Synthesis of New Zirconium Diketiminate Complexes and Catalytic Applications written by Ibrahim EL-Zoghbi and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Development of Late Transition Metal Insertion Polymerization Catalysts written by Tobias Friedberger and published by . This book was released on 2015 with total page 406 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polyolefins are the number one commercially produced polymeric material by volume, and find ubiquitous uses as plastics, elastomers, and fibers. They are produced from gaseous olefins such as ethylene and propylene by the action of a transition metal catalyst. Despite tremendous academic and industrial efforts and successes in catalyst development over the past decades, the copolymerization of polar functionalized olefins with sufficiently high activities still remains a largely unsolved issue. Late transition metal catalysts were shown to be more suitable for this kind of polymerization reaction due to their generally lower oxophilic character. The main goal of this thesis was the development of novel late transition olefin polymerization catalysts based on ruthenium and palladium. Prior to this work, only few active olefin polymerization Ru-catalysts were reported. Several series of complexes based on ruthenium were synthesized, characterized and investigated for olefin polymerization. Ru(II)-complexes of the type RuCl2(N,N,N)L with facially coordinating nitrogen donor ligands (N,N,N = trispyridyl-, trispyrazoyl-, trisimidazoyl-methane derivatives) were found to be inactive towards ethylene polymerization. Employing bisanionic disulfonate phosphines as ligands gave Ru-complexes that produced linear, high-molecular weight polyethylene in the presence of an aluminum-alkyl based cocatalyst. Increasing the electrophilicity of the complex, by decreasing the donor strength of the ligand and using higher oxidation state Ru(IV)-complexes, the polymerization activity could be increased, and one of the highest activities for any Ru-based catalyst was observed. Polar additives such as acetone fully inhibited even the most electron-rich catalysts and copolymerization reactions yielded no polymer. In a different approach to solve the same problem, Pd-diimine complexes were modified with pendant olefin and boronate groups. Pd-diimine complexes can facilitate the copolymerization of ethylene with acrylates, and interactions of the pendant Lewis acid group with the functional, Lewis basic comonomer was anticipated to increase catalyst activity. However, no effect of a pendant pinacol boronate was observed on the incorporation ratio of methyl acrylate in room temperature copolymerizations. The ability of the pendant olefin to coordinate to cationic Pd-species resulted in hemilabile effects. Increased catalyst stability at the cost of decreased activities was found in comparison with unfunctionalized ligands.
Download or read book Mechanisms in Homogeneous Catalysis written by Brian Heaton and published by John Wiley & Sons. This book was released on 2006-03-06 with total page 404 pages. Available in PDF, EPUB and Kindle. Book excerpt: While chemists using spectroscopic methods need to learn from the specialists, they do not normally read the spectroscopists' original papers. This book provides this very information -- summarizing some recent advances in the mechanistic understanding of metallocene polymerization catalysts and the role of NMR spectroscopy in these endeavors. Adopting a real practice-oriented approach, the authors focus on two of the most important spectroscopic techniques with two parts devoted to each of NMR and IR spectroscopy - as well as on important industrial applications with regard to the reaction discussed. Rather than providing a complete and exhaustive review of homogeneous hydrogenation and its detailed mechanisms, the book focuses on the specific spectroscopic techniques and the mechanistic information that has been obtained from their application. The result is unique in its scope, allowing chemists from different fields to learn which techniques can be applied for their specific synthetic problems. The prizewinning editor, Professor Brian Heaton, is the key player in the field, and has brought together here a team of authors to cater for specialists, and researchers in industry and academia.
Download or read book Metalorganic Catalysts for Synthesis and Polymerization written by Walter Kaminsky and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 674 pages. Available in PDF, EPUB and Kindle. Book excerpt: 45 years after the discovery of transition metals and organometallics as cocatalysts for the polymerization of olefins and for organic synthesis, these compounds have not lost their fascination. The birthday of Karl Ziegler, the great pioneer in this metalorganic catalysis, is now 100 years ago. Polyolefins and polydienes produced by Ziegler-Natta catalysis are the most important plastics and elastomers. New impulses for the polymerization of olefins have been brought about by highly active metallocenes and other single site catalysts. Just by changing the ligands of the organometallic compounds, the structure of the polymers produced can be tailored in a wide manner. In invited lectures and posters, relevant aspects of the metalorganic catalysts for synthesis and polymerization are discussed in this book. This includes mechanism and kinetics, stereochemistry, material properties, and industrial applications.
Download or read book Metal catalysis in Industrial Organic Processes written by Gian Paolo Chiusoli and published by Royal Society of Chemistry. This book was released on 2008 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt: A definitive reference source, written by practising experts in the field, providing detailed and up-to-date information on key aspects of metal catalysis.
Download or read book Late Transition Metal Polymerization Catalysis written by Bernhard Rieger and published by John Wiley & Sons. This book was released on 2006-03-06 with total page 345 pages. Available in PDF, EPUB and Kindle. Book excerpt: At the start of the 1950s, Ziegler and Natta discovered that simple metallorganic catalysts are capable of transforming olefins into linear polymers with highly ordered structures. This pioneering discovery was recognized with a Nobel Prize in 1963. In the 80s and 90s, the development of molecular defined metallocenes led to a renaissance for non-polar polyolefin materials. Designer catalysts allowed a greater precision in defining properties of the material. The past 10 years have seen the discovery of new catalysts based on late transition metals, which allow the combination of polar monomers with non-polar olefins and thus lead to innovative materials. Here, the world's leading authors from industry and academia describe the latest developments in this fascinating field for the first time in such comprehensive detail. In so doing, they introduce readers systematically to the basic principles and show how these new catalysts can effectively be used for polymerization reactions. This makes the book an ideal and indispensable reference for specialists, advanced students, and scientists of various disciplines dealing with research into catalysts and materials science.
